Light emitting diode light source

ABSTRACT

A light source that utilizes light emitting diodes that emit white light is disclosed. The diodes are mounted on an elongate member having at least two surfaces upon which the light emitting diodes are mounted. The elongate member is thermally conductive and is utilized to cool the light emitting diodes. In the illustrative embodiment, the elongate member is a tubular member through which a heat transfer medium flows. A cooling or fluid movement device coupled with the elongate thermally conductive member enhances cooling of the light emitting diodes.

RELATED APPLICATIONS

[0001] This application is a continuation-in-part of my co-pendingapplication Ser. No. 10/156,810 filed May 29, 2002.

FIELD OF THE INVENTION

[0002] This invention pertains to lighting sources, in general, and to alighting source that utilizes Light Emitting Diodes (LED's), inparticular.

BACKGROUND OF THE INVENTION

[0003] LED's have many advantages as light sources. However, in the pastLED's have found application only as specialized light sources such asfor vehicle brake lights, and other vehicle related lighting, andrecently as flashlights. In these prior applications, the LED's aretypically mounted in a planar fashion in a single plane that is disposedso as to be perpendicular to the viewing area. Typically the LED planararray is not used to provide illumination, but to provide signaling.

[0004] Recent attempts to provide LED light sources as sources ofillumination have been few, and generally unsatisfactory from a generallighting standpoint.

[0005] It is highly desirable to provide a light source utilizing LED'sthat provides sufficient light output so as to be used as a generallighting source rather than as a signaling source.

[0006] One problem that has limited the use of LED's to specialtysignaling and limited general illumination sources is that LED'stypically generate significant amounts of heat. The heat is such thatunless the heat is dissipated, the LED internal temperature will risecausing degradation or destruction of the LED.

[0007] It is therefore further desirable to provide an LED light sourcethat efficiently conducts heat away from the LED's.

SUMMARY OF THE INVENTION

[0008] In accordance with the principles of the invention, an improvedlight source is provided. The light source includes an elongatethermally conductive member having an outer surface. A plurality oflight emitting diodes is carried on the elongate member outer surface.At least some of the light emitting diodes are disposed in a first planeand others of said light emitting diodes are disposed in a second planenot coextensive with the first plane. Electrical conductors are carriedby the elongate thermally conductive member and are connected to theplurality of light emitting diodes to supply electrical power thereto.The elongate thermally conductive member conducts heat away from thelight emitting diodes to a thermally conductive fluid medium. A coolingdevice is utilized to remove heat from the light emitting diodes. In oneaspect of the invention, the cooling device comprises a fluid movingdevice utilized to cause the fluid medium to flow to cause cooling ofthe elongate thermally conductive member and therefore to dissipate heatfrom the light emitting diodes. In another aspect of the invention, thecooling device may be an electronic or solid state device such as aPiezoelectric device or a device that uses the Peltier effect, known asa Peltier device.

[0009] In the illustrative embodiment of the invention, the fluid mediumis air and the fluid moving device is an air moving device.

[0010] In accordance with one aspect of the invention, an illustrativeembodiment of the invention utilizes light emitting diodes that emitwhite light. However, other embodiments of the invention may utilizelight emitting diodes that are of different colors to producemonochromatic light or the colors may be chosen to produce white lightor other colors.

[0011] In accordance with another aspect of the invention the elongatethermally conductive member transfers heat from the light emittingdiodes to a medium within said elongate thermally conductive member. Inthe illustrative embodiment of the invention, the medium is air.

[0012] In accordance with another aspect of the invention, the elongatethermally conductive member has one or more projections or fins toenhance heat transfer to the medium. The projections or fins may bedisposed on the outer surface or inner surface of the elongate thermallyconductive member or may be disposed on both the outer and innersurfaces.

[0013] In accordance with another aspect of the invention the elongatethermally conductive member comprises a tube. In one embodiment of theinvention, the tube has a cross-section in the shape of a polygon. Inanother embodiment of the invention, the tube has a cross-section havingflat portions.

[0014] In accordance with another embodiment of the invention, theelongate thermally conductive member comprises a channel.

[0015] In accordance with the principles of the invention, the elongatethermally conductive member may comprise an extrusion, and the extrusioncan be highly thermally conductive material such as aluminum.

[0016] In one preferred embodiment of the invention the elongatethermally conductive member is a tubular member. The tubular member hasa polygon cross-section. However, other embodiments my have a tubularmember of triangular cross-section.

[0017] In one embodiment of the invention, a flexible circuit is carriedon a surface of said elongate thermally conductive member; the flexiblecircuit includes the electrical conductors.

[0018] In another aspect of the invention, the flexible circuitcomprises a plurality of apertures for receiving said plurality of lightemitting diodes. Each of the light emitting diodes is disposed in acorresponding one of the apertures and affixed in thermally conductivecontact with said elongate thermally conductive member.

[0019] The elongate thermally conductive member includes a thermaltransfer media disposed therein in a flow channel.

[0020] At least one clip for mounting the elongate thermally conductivemember in a fixture may be included.

BRIEF DESCRIPTION OF THE DRAWING

[0021] The invention will be better understood from a reading of thefollowing detailed description of a preferred embodiment of theinvention taken in conjunction with the drawing figures, in which likereference indications identify like elements, and in which:

[0022]FIG. 1 is a planar side view of a light source in accordance withthe principles of the invention;

[0023]FIG. 2 is a top planar view of the light source of FIG. 1;

[0024]FIG. 3 is a perspective view of the light source of FIG. 1 withmounting clips;

[0025]FIG. 4 is a planar side view of the light source of FIG. 3 showingmounting clips separated from the light source;

[0026]FIG. 5 is a top view of the light source and mounting clips ofFIG. 4;

[0027]FIG. 6 is a partial cross-section of the light source of FIG. 1;

[0028]FIG. 7 is a top view of an alternate elongate thermally conductivemember; and

[0029]FIG. 8 is a side view of the member of FIG. 7.

DETAILED DESCRIPTION

[0030] A light source in accordance with the principles of the inventionmay be used as a decorative lighting element or may be utilized as ageneral illumination device. As shown in FIG. 1, a light source 100 inaccordance with the invention includes an elongate thermally conductivemember or heat sink 101. Elongate heat sink 101 is formed of a materialthat provides excellent thermal conductivity. Elongate heat sink 101 inthe illustrative embodiment of the invention is a tubular aluminumextrusion. To improve the heat dissipative properties of light source100, elongate heat sink 101 is configured to provide convective heatdissipation and cooling. As more clearly seen in FIG. 2, tubular heatsink 101 is hollow and has an interior cavity 103 that includes one ormore surface discontinuities or heat dissipating protrusions 105. In theillustrative embodiment the surface discontinuities or heat dissipatingprotrusions 105 are triangular shaped fins, but may take on othershapes. In yet other embodiments, the surface discontinuities mayinclude apertures or blind bores either alone or in combinations withheat dissipation protrusions. Protrusions 105 are integrally formed onthe interior of elongate heat sink 101. In the illustrative embodimentmovement of a medium 102 through elongate heat sink 101 providescooling. Medium 102 utilized in the illustrative embodiment is air, butmay in some applications be a fluid other than air to provide forgreater heat dissipation and cooling.

[0031] Cooling device 199 is coupled to elongate thermally conductivemember 101 to enhance cooling of the LED's. Cooling device in oneembodiment of the invention is a medium moving device in fluid couplingwith elongate thermally conductive member 101 to enhance the movement ofmedium 102. Medium moving device 199 is utilized to enhance fluid medium102 to flow to cause cooling of the elongate thermally conductive memberand therefore to dissipate heat from the light emitting diodes. Mediummoving device 199 in a first illustrative embodiment is a fan and may bean electromechanical fan, electronic fan, or solid-state device such asa piezoelectric fan. In a second embodiment of the invention, coolingdevice 199 may comprise one or more solid state cooling devicesutilizing the Peltier effect, otherwise known as Peltier devices.Although cooling device 199 is shown at one end of the light source 100,it will be appreciated by those skilled in the art that where solidstate devices are utilized, a plurality of solid state devices may bepositioned at locations other than on an end of the light source 100. Itwill also be appreciated by those skilled in the art that solid statecooling devices such as Piezoelectric and Peltier devices are known.

[0032] The exterior surface 107 of elongate heat sink 101 has aplurality of Light Emitting Diodes 109 disposed thereon. Each LED 109 inthe illustrative embodiment comprises a white light emitting LED of atype that provides a high light output. Each LED 109 also generatessignificant amount of heat that must be dissipated to avoid thermaldestruction of the LED. As noted above cooling device 199 providescooling to avoid thermal destruction. By combining a plurality of LEDs109 on elongate thermally conductive member or heat sink 101, a highlight output light source that may be used for general lighting isprovided.

[0033] Conductive paths 129 are provided to connect LEDs 109 to anelectrical connector 111. The conductive paths may be disposed on anelectrically insulating layer 131 or layers disposed on exterior surface107. In the illustrative embodiment shown in the drawing figures, theconductive paths and insulating layer are provided by means of one ormore flexible printed circuits 113 that are permanently disposed onsurface 107. As more easily seen in FIG. 6, printed circuit 113 includesan electrically insulating layer 131 that carries conductive paths 129.As will be appreciated by those skilled in the art, other means ofproviding the electrically conductive paths may be provided.

[0034] Flexible printed circuit 113 has LED's 109 mounted to it in avariety of orientations ranging from 360 degrees to 180 degrees andpossibly others depending on the application. Electrical connector 111is disposed at one end of printed circuit 113. Connector 113 iscoupleable to a separate power supply to receive electrical current.Flexible printed circuit 113, in the illustrative embodiment is coatedwith a non-electrically conductive epoxy that may be infused withoptically reflective materials. Flexible printed circuit 113 is adheredto the tube 101 with a heat conducting epoxy to aid in the transmissionof the heat from LEDs 109 to tube 101. Flexible printed circuit 113 hasmounting holes 134 for receiving LEDs 109 such that the backs of LEDs109 are in thermal contact with the tube surface 107.

[0035] Tubular heat sink 101 in the illustrative embodiment is formed inthe shape of a polygon and may have any number of sides. Althoughtubular heat sink 101 in the illustrative embodiment is extrudedaluminum, tubular heat sink 101 may comprise other thermal conductivematerial. Fins 105 may vary in number and location depending onparticular LED layouts and wattage. In some instances, heat dissipationprotrusions or fins may be added to the exterior surface of tubular heatsink 101. In addition, apertures may be added to the tubular heat sinkto enhance heat flow.

[0036]FIGS. 7 and 8 show an alternate elongate thermally conductivemember 201 that has both exterior surface discontinuities or heatdissipation protrusions or fins 205 in addition to interior surfacediscontinuities or heat dissipation protrusions or fins 241.

[0037] Light source 100 is mounted into a fixture and retained inposition by mounting clips 121, 123 as most clearly seen in FIGS. 3, 4,and 5. Each of the clips is shaped so as to engage and retain lightsource 100. Each clip is affixed on one surface 122, 124 to a lightfixture.

[0038] Although light source 100 is shown as comprising elongate tubularthermally conductive members or heat sinks 101, 201, other extrudedelongate members may be used such as channels.

[0039] In the illustrative embodiment shown, cooling by flow of airthrough elongate thermally conductive members or tubular heat sinks 101,201 is utilized such that cool or unheated air enters elongate thermallyconductive members 101, 201 by fluid movement device 199, passes overthe surface discontinuities or heat dissipation protrusions, and exitsfrom the opposite end of elongate thermally conductive member 101, 201as heated air. In higher wattage light sources, rather than utilizingair as the cooling medium, other fluids may be utilized. In particular,convective heat pumping may be used to remove heat from the interior ofthe heat sink.

[0040] In one particularly advantageous embodiment of the invention, thelight source of the invention is configured to replace compactfluorescent lighting in decorative applications.

[0041] It will be appreciated by those skilled in the art that althoughthe invention has been described in terms of light emitting diodes, theinvention is equally applicable to other non-filament miniature lightssources such as organic light emitting diodes (OLED's) and polymer typelight sources. It is intended that the term “light emitting diode” or“LED” as used in the claims is intended to not be limited to solid statelight emitting diodes, but is intended to include such other miniaturelight sources.

[0042] It has further been determined that the uniformity of lightdistribution of a light source having an elongate thermally conductivemember with heat dissipation protrusions or fins 205 on the outersurface of the elongate thermally conductive member 201 is enhanced byutilization of an appropriately selected coating or treatment to theouter or exterior surfaces of elongate thermally conductive member 201.In particular, in a comparison of various surface coatings ortreatments, it has been found that the use of a non-reflective or blacksurface on the protrusions or fins 205 provides a more uniform lightoutput. It has been determined that the use of reflective or whitesurfaces on protrusions results in the protrusions producing shadows inthe light output.

[0043] As will be appreciated by those skilled in the art, theprinciples of the invention are not limited to the use of light emittingdiodes that emit white light. Different colored light emitting diodesmay be used to produce monochromatic light or to produce light that isthe combination of different colors.

[0044] Although the invention has been described in terms ofillustrative embodiments, it is not intended that the invention belimited to the illustrative embodiments shown and described. It will beapparent to those skilled in the art that various changes andmodifications may be made to the embodiments shown and described withoutdeparting from the spirit or scope of the invention. It is intended thatthe invention be limited only by the claims appended hereto.

What is claimed is:
 1. A light source comprising: an elongate thermallyconductive member having an outer surface; a plurality of light emittingdiodes carried on said elongate member outer surface at least some ofsaid light emitting diodes being disposed in a first plane and others ofsaid light emitting diodes being disposed in a second plane notcoextensive with said first plane; said elongate thermally conductivemember being configured to conduct heat away from said light emittingdiodes to fluid contained by said elongate thermally conductive member;said elongate thermally conductive member comprises one or more surfacediscontinuities to enhance heat dissipation; and a fluid movement devicein fluid communication with said elongate thermally conductive member toenhance movement of said fluid over at least some of said heat surfacediscontinuities.
 2. A light source in accordance with claim 1, wherein:said fluid movement device comprises an electromechanical device.
 3. Alight source in accordance with claim 2, wherein: said electromechanicaldevice comprises a fan.
 4. A light source in accordance with claim 1,wherein: said fluid movement device comprises an electronic device.
 5. Alight source in accordance with claim 1, wherein: said fluid movementdevice comprises a solid state device.
 6. A light source in accordancewith claim 1, wherein: said fluid movement device comprises anpiezoelectric device.
 7. A light source in accordance with claim 1,wherein: said elongate thermally conductive member is configured toconduct heat away from said light emitting diodes to fluid proximatesaid elongate member outer surface.
 8. A light source in accordance withclaim 7, wherein: said fluid proximate said elongate member outersurface comprises air.
 9. A light source in accordance with claim 7,wherein: said fluid movement device comprises an electromechanicaldevice.
 10. A light source in accordance with claim 9, wherein: saidelectromechanical device comprises a fan.
 11. A light source inaccordance with claim 7, wherein: said fluid movement device comprisesan electronic device.
 12. A light source in accordance with claim 7,wherein: said fluid movement device comprises a solid state device. 13.A light source in accordance with claim 12, wherein: said fluid movementdevice comprises an piezoelectric device.
 14. A light source inaccordance with claim 1, wherein: said fluid contained by said elongatethermally conductive member is a cooling medium other than air.
 15. Alight source in accordance with claim 1, wherein: said elongatethermally conductive member comprises a tube.
 16. A light source inaccordance with claim 15, wherein: said tube has a cross-section in theshape of a polygon.
 17. A light source in accordance with claim 6,wherein: said tube has a cross-section having flat portions.
 18. A lightsource in accordance with claim 1, wherein: said elongate thermallyconductive member comprises a channel.
 19. A light source in accordancewith claim 18, wherein: said elongate thermally conductive membercomprises an extrusion.
 20. A light source in accordance with claim 18,wherein: said extrusion is an aluminum extrusion.
 21. A light source inaccordance with claim 1, wherein: each of said light emitting diodesemits white light.
 22. A light source in accordance with claim 1,wherein: at least some of said light emitting diodes emit colored light.23. A light source comprising: an elongate thermally conductive memberhaving an outer surface; a plurality of light emitting diodes carried onsaid elongate member outer surface at least some of said light emittingdiodes being disposed in a first plane and others of said light emittingdiodes being disposed in a second plane not coextensive with said firstplane; said elongate thermally conductive member being configured toconduct heat away from said light emitting diodes to fluid contained bysaid elongate thermally conductive member; and a cooling apparatuscoupled to said elongate thermally conductive member to enhance coolingof said plurality of light emitting diodes.
 24. A light source inaccordance with claim 23, wherein: said cooling device comprises a solidstate cooling device.
 25. A light source in accordance with claim 23wherein: said cooling device comprises a Peltier device.
 26. A lightsource in accordance with claim 23 wherein: said cooling devicecomprises a Piezoelectric device.
 27. A light source comprising: anelongate thermally conductive member having an outer surface; at leastone light emitting diode carried on said elongate member outer surface;said elongate thermally conductive member being configured to conductheat away from said at least one light emitting diode; and a coolingapparatus coupled to said elongate thermally conductive member toenhance cooling of said at least one light emitting diode.
 28. A lightsource in accordance with claim 27, wherein: said cooling devicecomprises a solid state cooling device.
 29. A light source in accordancewith claim 27 wherein: said cooling device comprises a Peltier device.30. A light source in accordance with claim 27 wherein: said coolingdevice comprises a Piezoelectric device.
 31. A light source comprising:an elongate thermally conductive member having an outer surface; atleast one light emitting diodes carried on said elongate member outersurface; one or more electrical conductors carried by said elongatethermally conductive member and connected to said at least one lightemitting diodes to supply electrical power thereto; said elongatethermally conductive member being configured to conduct heat away fromsaid at least one light emitting diode to fluid contained by saidelongate thermally conductive member; and a fluid moving device in fluidcommunication with said elongate thermally conductive member to movesaid fluid.
 32. A light source comprising: an elongate thermallyconductive member having an outer surface; a plurality of light emittingdiodes carried on said elongate member outer surface at least some ofsaid light emitting diodes being disposed in a first plane and others ofsaid light emitting diodes being disposed in a second plane notcoextensive with said first plane; electrical conductors carried by saidelongate thermally conductive member and connected to said plurality oflight emitting diodes to supply electrical power thereto; and saidelongate thermally conductive member being configured to conduct heataway from said light emitting diodes to fluid contained by said elongatethermally conductive member; and a coating carried on said elongatethermally conductive member.
 33. A light source in accordance with claim32, wherein: said coating is infused with optically reflective material.